Automotive vacuum pump

ABSTRACT

An automotive vacuum pump includes a housing arrangement which encloses a pumping chamber and which rotatably supports a pump rotor having a rotor body with a bearing section and a vane section. The vane section of the rotor body has a vane slit. A slidable pump vane is supported in the vane slit. The slidable pump vane separates the pumping chamber into a plurality of rotating pumping compartments. The housing arrangement has a pumping chamber gas inlet opening and a pumping chamber gas outlet opening. The rotor body further has a separate oil outlet opening which is open to the pumping chamber

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/062285, filed on Jun. 2, 2015. The International Application was published in English on Dec. 8, 2016 as WO 2016/192782 A1 under PCT Article 21(2).

FIELD

The present invention is directed to an automotive vacuum pump which is lubricated with oil. The present invention can, for example, be directed to a mechanical automotive vacuum pump which is mechanically driven by an internal combustion engine.

BACKGROUND

An automotive vacuum pump is provided with a housing arrangement which encloses a pumping chamber and rotatably supports a pump rotor with a pump rotor body. The pump rotor body can be separated in axial direction into two functional sections, namely, a bearing section and a vane section. In the bearing section, the rotor body is radially supported rotatably at the pump housing arrangement. In the vane section, the rotor body is provided with at least one vane slit wherein at least one slidable pump vane is slidably supported. The pump vane or the pump vanes separate the pumping chamber into several rotating pumping compartments.

The housing arrangement is provided with a pumping chamber gas inlet opening through which gas flows into the pumping chamber, and with a pumping chamber gas outlet opening through which compressed gas leaves the pumping chamber. The gas inlet opening and the gas outlet opening are in most cases provided in a pump chamber front end wall which lies in a radial plane perpendicular to the rotational axis of the pump rotor.

The vacuum pump is supplied with pressurized oil which is used to improve the pneumatic performance and, in case of a mechanical vacuum pump, is also used to lubricate the mechanical coupling of the vacuum pump. A particular amount of oil is supplied into the pumping chamber so that not only gas, but also oil, must be discharged from the pumping chamber to avoid extensive vibrations and a deformation of the pump vane in the final discharge phase of the respective pumping compartment.

The oil is discharged together with the gas through one single combined gas and oil outlet opening in state-of-the-art vacuum pumps. It is also known to provide a separate oil outlet opening in a front end wall of the housing arrangement. The separate oil outlet opening is arranged behind the gas outlet opening, as seen in the direction of rotation. The oil outlet opening is therefore relatively small so that the flow and pressure conditions during the oil discharge phase can be dramatic, in particular at high rotational speed.

SUMMARY

An aspect of the present invention is to provide an automotive vacuum pump with smoother oil discharge characteristics.

In an embodiment, the present invention provides an automotive vacuum pump which includes a housing arrangement which is configured to enclose a pumping chamber and to rotatably support a pump rotor comprising a rotor body which comprises a bearing section and a vane section. The vane section of the rotor body comprises a vane slit. A slidable pump vane is supported in the vane slit. The slidable pump vane is configured to separate the pumping chamber into a plurality of rotating pumping compartments. The housing arrangement comprises a pumping chamber gas inlet opening and a pumping chamber gas outlet opening. The rotor body further comprises a separate oil outlet opening which is open to the pumping chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a cross-section of a mechanical automotive vacuum pump including a pump rotor with two oil outlet openings;

FIG. 2 shows a longitudinal section of the vacuum pump of FIG. 1;

FIG. 3 shows a longitudinal section of the pump rotor of the vacuum pump of FIGS. 1 and 2; and

FIG. 4 shows a plan view of the bearing section including a coupling structure of the pump rotor of the vacuum pump of FIGS. 1 and 2.

DETAILED DESCRIPTION

The automotive vacuum pump according to the present invention is provided with a rotor body which is provided with a separate oil outlet opening which is open to the pumping chamber and through which the oil is discharged from the rotating pumping compartment in the final compression phase of the respective pumping compartment. The oil outlet opening is not provided in a static housing wall, but is co-rotatably provided at the rotor body. The gas outlet opening can, for example, be arranged at a static side wall of the pump housing arrangement. The gas outlet opening and the separate oil outlet opening are therefore no longer in conflict with respect to the available surface. The opening angle of the oil outlet opening can be increased significantly since the oil outlet opening is not provided at the housing. Since the opening angle of the oil outlet opening is increased, there is more time to discharge the oil from the rotating pumping compartment in the final compression phase of the pumping compartment. The oil discharge process is therefore smoother, in particular at a high rotational speed of the pump rotor. This leads to decreased noise, decreased vibration, and a decreased wear out of the mechanical components.

The gas openings are in fluidic connection with a pump gas inlet and with a pump gas outlet, respectively. It is not excluded that oil flows through a gas opening. The oil outlet opening has the main function to lead oil to a separate oil outlet, not to the pump gas outlet. But it cannot be excluded that gas is also discharged through the oil outlet opening.

In an embodiment of the present invention, the oil outlet opening can, for example, be provided in the longitudinal cylindrical vane section of the rotor body. The oil outlet opening is not provided in the bearing section of the rotor body. The complete oil outlet opening can, for example, be provided in the cylindrical vane section of the rotor body.

In an embodiment of the present invention, the pumping chamber can, for example, be covered by two front end walls both lying in a radial plane so that the end walls are lying in a plane perpendicular to the rotational axis of the pump rotor. The oil outlet opening is provided adjacent to one end wall, and is in particular provided adjacent to the front end wall which lies below the other end wall, with respect to the vector of gravitation, when the vacuum pump is mounted in an automobile. The oil outlet opening can, for example, be placed as close as possible to the bottom plane of the rotor to minimize the pressure drop all along the rotor's internal duct. The oil outlet opening can, for example, be arranged at the lowest point of the pumping chamber in the final phase of the compression interval of the respective pumping compartment. This arrangement of the oil outlet opening provides that the oil volume which is accumulated at the lowest gravitational location within the rotating pumping compartment can directly be discharged via the oil outlet opening when the rotating oil outlet opening arrives at the final compression phase of the respective pumping compartment.

In an embodiment of the present invention, the oil outlet opening can, for example, be provided in the lagging third of the respective pumping compartment, for example, in the lagging fourth of the respective pumping compartment. The oil outlet opening therefore arrives at the final compression zone right before the vane head arrives at the commutation sector which is the liquid-tight sector between the gas outlet opening and the gas inlet opening, as seen in the direction of rotation. In other words, the oil outlet opening is arranged in that sector of the respective pumping compartment which arrives at last at the gas-tight commutation sector.

In an embodiment of the present invention, the opening angle of the oil outlet opening can, for example, be smaller than the angle of the gas-tight commutation sector between the gas outlet opening and the gas inlet opening so that the oil outlet opening cannot define a fluidic bypass with respect to the commutation sector. The opening angle of the white outlet opening is an angle lying in a radial plane and with the sector center lying in the rotational axis of the pump rotor.

In an embodiment of the present invention, the pump rotor can, for example, be provided with a coupling structure at one axial coupling end of the rotor body. The coupling structure can, for example, be provided at one axial coupling end which is defined by the bearing section of the rotor body. The rotor body is provided with an oil conduct which fluidically connects the oil outlet opening to the axial coupling end. As a result, the coupling structure is directly lubricated with the oil which is discharged via the oil outlet opening.

In an embodiment of the present invention, the oil discharge opening can, for example, be provided with a check-valve so that a backflow of the oil in a direction from the axial coupling structure and back to the oil outlet opening is avoided.

In an embodiment of the present invention, the vacuum pump can, for example, be provided as a single-vane pump with one single pump vane which can have two vane parts which are slidable to each other. The single vane is supported by the single vane slit which radially penetrates the rotor body. At least two oil outlet openings are provided at the rotor body, one oil outlet opening in each pumping compartment.

An embodiment of the present invention is described below under reference to the drawings.

The drawings show a mechanical automotive vacuum pump 10 which provides an absolute pressure of below 100 mbar for supplying, for example, a pneumatic breaking force device with low pressure. The vacuum pump 10 is mechanically driven by an automotive engine, for example, by an internal combustion engine.

The vacuum pump 10 comprises a static housing arrangement 12 which supports and substantially houses a rotatable pump rotor 14. The housing arrangement 12 comprises a complex and pot-shaped housing main body 11 for radially enclosing and rotatably supporting the pump rotor 14 and comprises a separate housing cover lid 13 for axially closing one axial end of the housing arrangement 12.

The pump rotor 14 comprises a plastic pump rotor body 30 with a substantially cylindrical and stepless outer surface over the entire axial length of the pump rotor body 30. The pump rotor body 30 is axially provided with two functional partitions, namely, the vane section 16 with a vane slit 32, and the bearing section 18 where the pump rotor body 30 is rotatably supported at the housing body 11 by a frictional bearing. The vane slit 32 supports a radially shiftable pump vane 33 which is defined by one single vane body 34 which co-rotates with the pump rotor body 30.

The housing arrangement 12, which is defined by the housing body 11 and the housing lid 13, encloses a pumping chamber 17 wherein the pump vane 33 rotates. The housing lid 13 defines one axial front end wall 64, and a ring-like portion of the housing body 11 defines a ring-like front end wall 62 of the pumping chamber 17. The pump vane 33 separates the pumping chamber 17 into two pumping compartments 171, 172 which rotate when the pump rotor 14 rotates.

In the bearing section 18, the pump rotor body 30 is provided with a cylindrical bearing surface which defines a radial friction bearing together with a corresponding cylindrical bearing surface of the housing main body 11. The pump rotor 14, in this embodiment, is supported by only one radial friction bearing so that the body of the pump rotor 14 is supported cantilevered. The bearing-sided axial coupling end 72 of the pump rotor 14 is provided with a bearing ring surface which is axially supported by a corresponding axial bearing ring surface defined by the housing main body 11. The two bearing ring surfaces together define an axial friction bearing. As shown in FIG. 4, the bearing-sided coupling end 72 of the pump rotor 14 is provided with a coupling structure 70 for coupling a corresponding coupling structure of a pump drive. The other front end of the pump rotor body 30 is axially supported by the housing lid 13.

The bearing-sided ring-like front end wall 62 is provided with a sickle-shaped gas inlet opening 26 and with a sickle-shaped gas outlet opening 22. The gas inlet opening 26 is fluidically connected to a pump inlet 28 via a gas inlet channel 27. The gas outlet channel is fluidically connected to a pump outlet via a gas outlet channel 23. The gas inlet channel 27 and the gas outlet channel 23 are defined as bores in a ring body section 20 of the housing body 11.

Seen in a circumferential direction, a commutation sector 60 is defined between the gas outlet opening 22 and the gas inlet opening 26 (see FIG. 1). In the commutation sector 60, the pump rotor body 30 is arranged directly adjacent to the circumferential wall 80 of the housing body 11 so that the commutation sector 60 defines a gas-tight section, thereby avoiding a flow-back of compressed gas. The commutation width of the commutation sector 60, seen in a circumferential direction, is equal or larger than the thickness of the vane body 34 or of the vane slit 32.

The pump rotor body 30 is provided with two separate oil outlet openings 40, 40′ defined by outlet recesses 41, 41′ which are both radially orientated and open to the respective pumping compartment 171, 172. The oil outlet openings 40, 40′ both respectively lie in a cylindrical plane defined by the cylindrical outer surface of the pump rotor body 30. In the shown embodiment, the pump rotor 14 rotates in a clockwise direction so that the oil outlet openings 40, 40′ are both arranged in the lagging fourth of the respective rotating pumping compartment 171, 172 so that the respective oil outlet opening 40, 40′ arrives at the commutation sector 60 in the final part of the compression phase of the respective pumping compartment 171, 172. The opening angle 66 of the oil outlet openings is slightly smaller than the commutation sector angle 67 of the commutation sector 60 where the cylindrical commutation slit is gas-tight. The oil outlet openings 40, 40′ are both provided axially adjacent to the ring-like front end wall 62 which is provided with the gas outlet opening 22 and the gas inlet opening 26. FIG. 2 shows an orientation of the vacuum pump 10 when the vacuum pump 10 is mounted in an automobile. The ring-like front end wall 62 can, for example, lie below the other front end wall 64 so that oil is collected at the ring-like front end wall 62 due to gravity.

The oil outlet openings 40, 40′ are fluidically connected with corresponding oil discharge openings 44, 44′ which are located at the axial coupling end 72 of the pump rotor body 30. The oil outlet opening 40, 40′ and the corresponding oil discharge openings 44, 44′ are connected by respective oil ducts 42, 42′, 43, 43′, which are a radial bore duct 42, 42′ and an axial bore duct 43, 43′.

Both oil discharge openings 44, 44′ are provided with a check valve 76, 76′, respectively, which comprises a sheet-like valve body 45, 45′ and a valve stop 46, 46′ which limits the opening movement of the valve body 45, 45′. The valve body 45, 45′ is defined by a sheet-like flexible tongue and opens the oil discharge openings 44, 44′ when the pressure of the fluid in the respective oil outlet opening 40, 40′ is above an opening pressure difference which is, for example, 100 mbar.

When the pump 10 is in use and the pump rotor 14 is rotating, gas, in particular, air, is sucked through the pump inlet 28 and the gas inlet opening 26 into the rotating pumping compartment 172 at the suction side. The gas is transported in the rotating pumping compartment 172 to the compression side so that the compressed gas is pumped through the gas outlet opening 22 to the pump outlet 24. The pump outlet 24 can be provided with a check valve which avoids a flow back of gas into the pumping chamber 17.

During all pumping phases, a limited amount of oil is pumped into the interior of the pump 10 so that oil is also accumulated within the pumping chamber 17. The oil in the pumping chamber 17 is in particular accumulated at the bottom ring-like front end wall 62 and is accumulated in the remaining volume of the compression-sided pumping compartment 171 in the final compression phase. As soon as the fluid pressure in the pumping compartment 172 is higher than the atmospheric counter pressure plus the opening pressure difference, the corresponding check valve 76 opens and the oil is discharged to the area of the coupling structure 70.

The check valve 76 closes as soon as the oil outlet opening 40 is completely covered by the circumferential wall 80 in the commutation sector 60.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 

What is claimed is: 1-8. (canceled)
 9. An automotive vacuum pump comprising: a housing arrangement configured to enclose a pumping chamber and to rotatably support a pump rotor comprising a rotor body which comprises a bearing section and a vane section, wherein, the vane section of the rotor body comprises a vane slit, a slidable pump vane is supported in the vane slit, the slidable pump vane being configured to separate the pumping chamber into a plurality of rotating pumping compartments, the housing arrangement comprises a pumping chamber gas inlet opening and a pumping chamber gas outlet opening, and the rotor body further comprises a separate oil outlet opening which is open to the pumping chamber.
 10. The automotive vacuum pump as recited in claim 9, wherein, the rotor body further comprises a longitudinal cylindrical vane section, and the separate oil outlet opening is arranged in the longitudinal cylindrical vane section of the rotor body.
 11. The automotive vacuum pump as recited in claim 9, wherein, the pumping chamber is covered by two front end walls which are each arranged to lie in a radial plane, and the separate oil outlet opening is arranged adjacent to one of the two front end walls.
 12. The automotive vacuum pump as recited in claim 9, wherein, the separate oil outlet opening is arranged in a lagging third or in a lagging fourth of a respective rotating pumping compartment.
 13. The automotive vacuum pump as recited in claim 9, further comprising: a gas-tight commutation sector arranged between the pumping chamber gas outlet opening and the pumping chamber gas inlet opening, the gas-tight commutation sector comprising a commutation sector angle, wherein, the separate oil outlet opening comprises a separate oil outlet opening angle, the commutation sector angle is larger than the separate oil outlet opening angle, and each of the commutation sector angle and the separate oil outlet opening angle are seen from a center of the rotor body perpendicular to an axis of rotation of the rotor body.
 14. The automotive vacuum pump as recited in claim 9, wherein, the pump rotor further comprises a coupling structure arranged at an axial coupling end of the rotor body, and the rotor body further comprises an oil duct which fluidically connects the separate oil outlet opening to the axial coupling end.
 15. The automotive vacuum pump as recited in claim 14, wherein, the axial coupling end comprises an oil discharge opening which is fluidically connected to the separate oil outlet opening, and the oil discharge opening comprises a check-valve.
 16. The automotive vacuum pump as recited in claim 9, wherein, one slidable pump vane comprising one vane body is supported in the vane slit which is configured to radially penetrate the rotor body, and the rotor body comprises two separate oil outlet openings, one of the separate oil outlet openings being arranged in each rotating pumping compartment. 